Heat exchanger

ABSTRACT

A core plate of header tanks in a heat exchanger includes a tube joint portion on which a plurality of tube insertion holes is formed, a receiving portion surrounding the tube joint portion and housing a tip part adjacent to the core plate in the tank body portion, and a inclined portion connecting between the receiving portion and the tube joint portion and inclined with respect to a longitudinal direction of the tube. The inclined portion is provided on the core plate such that a first virtual line extending linearly along the inclined portion from the receiving portion toward the tube joint portion and a second virtual line extending linearly along the tube joint portion in a direction of a long diameter in a cross section of the tube are intersected outside of the tube in the width direction of the tube.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on Japanese Patent Application No. 2015-142835 filed on Jul. 17, 2015, disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger, and is preferable for a radiator for cooling water of a water-cooled internal combustion engine.

BACKGROUND ART

A conventional heat exchanger has a core portion in which a plurality of tubes and a plurality of corrugated fins are alternately stacked, and a header tank joined to an end part of the tube in the longitudinal direction of the tube and communicating with the tube, and or the like. The header tank has a core plate into which the tube is inserted, and a tank body portion a tip part of which is fixed to the core plate, forming an internal space of the header tank together with the core plate. The core plate has a flat surface on the inner side of the header tank, a tube joint portion provided with a tube insertion hole into which a plurality of tubes are inserted, and a groove provided on the outside of the tube joint portion and configured to receive the end part of the tank body portion.

In the heat exchanger of this type, when a temperature difference occurs between adjacent one of the tubes, the tube joint part in the core plate is deformed. There is a problem that the stress is concentrated on the end part in a tube width direction of the tube.

For example, in the patent literature 1, a part on the end part side in the width direction of the tube at the periphery of the tube insertion hole is formed as a shape protruding toward the upper side. The patent literature 1 having this configuration improves the strength on the end side of the tube in the width direction of the tube.

PRIOR ART LITERATURES Patent Literature

Patent Literature 1: International Publication WO No. 2014/180865

SUMMARY OF INVENTION

In the heat exchanger such as a radiator mounted on the vehicle, it is desired to make the thickness in the width direction of the tube as the flow direction of the air as thin as possible due to a restriction on mounting. To achieve such a demand, it is necessary to reduce the thickness in the width direction of the tube in the core plate of the heat exchanger.

Here, FIG. 12 illustrates a schematic cross sectional view showing the core plate which is firstly studied by the present inventors. FIGS. 13 and 14 illustrate a schematic cross sectional view showing the core plate which is secondly studied by the present inventors. A structure shown in FIG. 12 is referred to as a studied example 1, and a structure shown in FIGS. 13 and 14 is referred to as a studied example 2.

As shown in the studied example 1 in FIG. 12, if the thickness in the width direction WD of the tube TB of the core plate CP1 is thinned (from LW1 to LW2), a wall surface of the core plate CP1 and a wall surface of the tube TB which faces the wall surface of the core plate are close to each other in the width direction of the tube TB.

When the tube TB and the core plate CP1 are brazed and joined, the brazing material is easily around not only at a peripheral portion of a tube insertion hole TBh but also between the opposed wall surfaces of the core plate CP1 and the tube TB. Thus, there is a possibility that the tube TB and the core plate CP1 may be joined at unintended positions.

On the other hand, as shown in the studied example 2 of FIG. 13, the present inventors studied the structure in which an interval between the opposite wall surfaces of the core plate CP2 and the tube TB was expanded at a position other than at the periphery of the tube insertion hole TBh. Namely, as shown in FIG. 14, an inclined portion Ci is provided between a joint part Cj connected to the tube TB in the core plate CP2 and a part Ct for receiving the tank body portion. Thus, even if the thickness in the width direction WD of the tube TB in the core plate CP2 of the heat exchanger is thinner, it is possible to prevent the tube TB and the core plate CP2 from being joined at unintended positions.

However, when the structure shown in FIG. 14 is actually experimentally produced, a recess (namely, a sink) Cs is formed at the peripheral edge part of the tube insertion hole TBh in the core plate CP2. Due to the unintended recess Cs, when the tube TB and the core plate CP2 are brazed and joined, an infiltrating of the brazing material is not stabilized, and the connection state between the tube TB and the core plate CP2 becomes unstable.

The present inventors investigated a cause of the formation of the recess Cs in the core plate CP2. As a result, in the structure shown in the studied example 2, since the tube insertion hole TBh is formed on a part of the inclined portion Ci of the core plate CP2 having a thickness larger than that of the tube joint portion Cj, the recess Cs is formed due to a die shrinkage when the tube insertion hole TBh is formed.

It is an object of the present disclosure to provide a heart exchanger in which an occurrence of the unintended recess on the core plate can be prevented, even if the thickness in the width direction of the tube in the core plate is thinner.

According to one aspect of the present disclosure, the heat exchanger includes a core portion having a plurality of tubes formed as a flat shape and arranged in stack with each other, and header tanks provided on an end part of the tube in a tube longitudinal direction of the tube and communicating with the plural tubes.

The header tanks in the heat exchanger include a core plate brazed and joined to the plural tubes in a state that the end part of the tube in the tube longitudinal direction of the tube is inserted in a plurality of tube insertion holes, and a tank body portion fixed to the core plate and forming a space communicating with a plurality of tubes together with the core plate.

The core plate includes a tube joint portion in which the plurality of tube insertion holes are formed, a receiving portion surrounding the tube joint portion and housing a tip part which is close to the core plate in the tank body portion, and an inclined portion connected between the receiving portion and the tube joint portion and inclined with respect to the longitudinal direction of the tube.

The inclined portion is provided on the core plate such that an intersection between a first virtual line and a second virtual line is positioned outside in the width direction of the tube, wherein the first virtual line is defined as extending linearly along the inclined portion from the receiving portion toward the tube joint portion and the second virtual line is defined as extending linearly along the tube joint portion in a direction of a long diameter in a cross section of the tube.

Thus, since the first virtual line extending along the inclined portion of the core plate and the second virtual line extending along the tube joint portion are intersected outside in the tube width direction of the tube, the inclined portion is formed at a position away from the tube insertion hole in the width direction of the tube. Therefore, the recess occurred at the peripheral part of the tube insertion hole in the core plate due to a die shrinkage at the time of forming the tube insertion hole can be prevented.

Accordingly, according to the heat exchanger in the present disclosure, even if the thickness in the width direction of the tube in the core plate is thinner, it is possible to suppress the occurrence of unintended recess on the core plate. As a result, when the tube and the core plate are brazed and joined, a wraparound of the brazing material is stabilized, and a joining state between the tube and the core plate can be stable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a schematic front view of a radiator in a first embodiment;

FIG. 2 is a diagram illustrating a perspective view of main part including header tanks of the radiator in the first embodiment;

FIG. 3 is a diagram illustrating a front view of a core plate of the radiator in the first embodiment;

FIG. 4 is a diagram illustrating a bottom view of the core plate of the radiator in the first embodiment;

FIG. 5 is a diagram illustrating a cross sectional view taken along line V-V in FIG. 4;

FIG. 6 is a diagram illustrating a cross sectional view taken along line VI-VI in FIG. 5;

FIG. 7 is a diagram illustrating a cross sectional view of a main part of the core plate in the radiator in the first embodiment;

FIG. 8 is an explanatory diagram showing a deformation state of the core plate in the radiator in the first embodiment;

FIG. 9 is an explanatory diagram showing a deformation state of the core plate in the radiator in a comparative example;

FIG. 10 is a diagram showing a relationship between a tube-intersection distance and a stress generated on a tube root portion;

FIG. 11 is a diagram illustrating a cross sectional view of main part of the core plate in the radiator in a second embodiment;

FIG. 12 is a cross sectional view showing a state in which a tube is joined to a core plate in a studied example 1;

FIG. 13 is a cross sectional view showing a state in which a tube is joined to a core plate in a studied example 2; and

FIG. 14 is a diagram illustrating a cross sectional view of the core plate in the studied example 2.

EMBODIMENTS FOR CARRYING OUT INVENTION

Plural embodiments in the present disclosure are explained below with reference to the drawings. In each of the following embodiments, a part that corresponds to a matter described in the preceding embodiment may be assigned with the same reference numeral, and the description thereof may be omitted.

In each embodiment, if only part of the components is explained, the other parts of the components can be applied by the components explained in the preceding embodiments.

In the following embodiments, if no hindrance in combination occurs, each embodiment can be partially combined, even if not explicitly stated.

First Embodiment

The present embodiment is explained with reference to FIGS. 1 to 10. In the present embodiment, a heat exchanger according to the present disclosure is explained as a radiator 1 for cooling a water-cooled internal combustion engine mounted on a vehicle.

First, the basic configuration of a radiator 1 in the present embodiment is explained with reference to FIG. 1. As shown in FIG. 1, the radiator 1 has a core portion 10 which is a heat exchange part for heat exchange with cooling water of an internal combustion engine (not shown) with an outside air. The core portion 10 is formed as a stacked body in which each of plural tubes 11 and each of plural fins 12 are alternately stacked in a vertical direction. In the present embodiment, a direction in stacking each tube 11 and each fin 12 is referred to as a tube stacking direction YD.

Each tube 11 has a flow passage in which the cooling water in the internal combustion engine (not shown) flows. Each tube 11 in the present embodiment has a longitudinal direction so as to extend along a horizontal direction, and is formed as a flat shape having a long diameter in a cross section, a direction of which extends along a flowing direction of the outside air (referred to as a long diameter direction in the cross section).

Here, the flat shape includes an oval shape composed of a curved shape in which an arc part having a large radius of curvature and an arc part having a small radius of curvature are connected to each other, an elliptical shape having a shape in which the circular arc part and the flat part are combined, and the like. In the present embodiment, for convenience of explanation, a longitudinal direction of the tube 11 is referred to as a tube longitudinal direction XD, and a direction orthogonal to the tube longitudinal direction XD and the tube stacking direction YD is referred to as a tube width direction ZD. The tube width direction ZD of the present embodiment is a same direction with respect to a direction of the long diameter of the tube 11 (namely, the long diameter direction in the cross section).

The fin 12 increases the heat transfer area with the outside air, and increases the heat exchange between the outside air and the cooling water. The fin 12 in the present embodiment is formed as a corrugated shape, and is connected to the flat surfaces on both sides of the tube 11. In the present embodiment, the flat surface means that it is in a substantially flat state. In other words, the flat surface in the present embodiment includes minute steps, unevenness, and the like which are formed during production. A flat surface of a tube joint portion 211 and a flat surface of an inclined portion 215, which are later explained, are similar to the flat surface in the present embodiment.

Each of the tubes 11 and the fins 12 in the present embodiment are made of a metal having a good thermal conductivity, corrosion resistance, and the like (for example, an aluminum alloy). In the radiator 1 of the present embodiment, each tube 11, a fin 12, a core plate 21 to be later explained, and a side plate 40 to be later explained are integrally brazed and joined by a coated brazing material at a predetermined place of each member.

A pair of header tanks 20, 30, each of which has a space inside, are arranged at both end parts of each tube 11 in the tube longitudinal direction XD, and extends along the tube stacking direction YD. Each of header tanks 20, 30 is joined in such a manner that an end part of each tube 11 in the tube longitudinal direction XD is inserted in a tube insertion hole 211 a. An internal passage in each tube 11 communicates with a space formed inside of each of the header tanks 20, 30.

One of a pair of header tanks 20, 30 is configured as an inlet side tank 20, which distributes and supplies a high-temperature cooling water flowing out from the internal combustion engine (not shown) to each tube 11. The inlet side tank 20 includes an inflow port pipe 20 a connected to an outlet side of the cooling water of the internal combustion engine via a hose (not shown).

The other of a pair of header tanks 20, 30 is configured as an outlet side tank 30, which collects the cooling water cooled by the heat exchange with the outside air in the core portion 10 and discharges it. The outlet side tank 30 includes an outflow port pipe 30 a connected to an inlet side of the cooling water of the internal combustion engine via a hose (not shown).

Side plates 40 for reinforcing the core portion 10 are arranged at both end parts of the core portion 10 in the tube stacking direction YD. The side plates 40 extend along the tube longitudinal direction XD, both ends of the side plates are connected to each of the header tanks 20, 30. The side plates in the present embodiment are made of a metal such as an aluminum alloy etc.

Next, a detailed structure of each of the header tanks 20, 30 is explained with reference to FIGS. 2 to 7. As shown in FIG. 2, each of the header tanks 20, 30 has a core plate 21 which is joined in a state that the tube 11 is inserted, a tank body portion 22 which forms an inner space 20 b of each of the header tanks 20, 30 together with the core plate 21, and a packing 23.

The core plate 21 in the present embodiment is made of a metal having a good thermal conductivity, corrosion resistance, and the like (for example, an aluminum alloy). A tank body portion 22 in the present embodiment is made of a resin such as glass-reinforced polyamide reinforced with glass fiber. Further, the packing 23 is made of an elastically deformable rubber. The packing 23 may be made of for example, a silicone rubber or an EPDM (that is, an ethylene, a propylene, a diene rubber).

In the present embodiment, after the packing 23 is interposed between the core plate 21 and the tank body portion 22, a protruding part 213 of the core plate 21 (later explained) is plastically deformed so as to be pressed against the tank body portion 22, and the tank body portion 22 is caulked and fixed to the core plate 21

The core plate 21 has a tube joint portion 211 for joining the tube 11, and a receiving portion 212 which receives a flange part 222 of the tank body portion 22 (later explained) and the packing 23 around the tube joint portion 211.

The receiving portion 212 has two wall surfaces, and formed as L-shape. In other words, the receiving portion 212 has a bottom wall portion 212 a extending in the tube width direction ZD, and an outer side wall portion 212 b bending L-shaped from the bottom wall portion 212 a and extending in the tube longitudinal direction XD, when viewed from the tube stacking direction YD. As shown in FIG. 3, a plurality of protruding parts 213 for caulking are formed on the end part of the outer side wall portion 212 b of the receiving portion 212.

As shown in FIG. 4, in the tube joint portion 211, plural tube insertion holes 211 a are formed so as to be arranged at a predetermined interval in the tube stacking direction YD in such a manner that each tube 11 are brazed and joined in a state where the end part XD of the tube 11 in the tube longitudinal direction is inserted.

Here, FIG. 5 is a cross sectional view for showing a cross-sectional shape of the core plate 21, when a region including the tube insertion hole 211 a in the tube joint portion 211 is cut in the tube longitudinal direction XD. FIG. 6 is a cross sectional view for showing a cross-sectional shape of the core plate 21, when a region positioned between the tube insertion holes 211 a in the tube joint portion 211 is cut in the tube longitudinal direction XD.

As shown in FIG. 5, a burring portion 211 b is formed at a part extending in the tube width direction ZD in a peripheral edge part of the tube insertion hole 211 a and projects toward the inner space side of each header tank 20, 30. The burring portion 211 b is provided to increase the rigidity of the peripheral edge part of the tube insertion hole 211 a in the core plate 21.

Further, as shown in FIG. 6, the tube joint portion 211 has a rib 214 positioned between adjacent ones of the tube insertion holes 211 a and in a position corresponding to an end part of each tube 11 in the tube width direction ZD, and the rib 214 is recessed away from the end part of each tube 11 in the tube longitudinal direction XD.

The rib 214 is formed so as to be overlapped with the end part of each tube 11, in the tube width direction ZD, in the tube longitudinal direction XD, when viewed from the tube stacking direction YD (that is, a direction perpendicular to the paper surface of FIG. 5 and FIG. 6).

In the core plate 21 of the present embodiment the tube joint portion 211 and the receiving portion 212 are connected through an inclined portion 215 inclined with respect to the tube longitudinal direction XD. The core plate 21 has a portion formed as a stepped shape between the tube joint portion 211 and the bottom wall portion 212 a of the receiving portion 212.

The inclined portion 215 of the present embodiment inclines in such a manner that a distance in the tube width direction ZD between the inclined portion 215 and the tube 11 becomes narrower from a side of the bottom wall portion 212 a toward a side of the tube joint portion 211.

According to the knowledge of the present inventors, an unintended recess is easily formed at the peripheral edge part of the tube insertion hole 211 a in the tube joint portion 211, if the tube insertion hole 211 a is overlapped with a part of the inclined portion 215 in the tube longitudinal direction XD.

In the present embodiment, the inclined portion 215 is formed in such a manner that a part of the inclined portion 215 is not overlapped with the tube insertion hole 211 a in the tube longitudinal direction XD.

In detail, as shown in FIG. 7, the inclined portion 215 is formed in such a manner that a first virtual line VL1 extending linearly along the inclined portion 215 and a second virtual line VL extending linearly along the tube joint portion 211 intersect outside in the tube width direction ZD of the tube 11. In other words, the inclined portion 215 in the present embodiment is formed on the core plate 21 in such a manner that an intersection A between the first virtual line VL1 and the second virtual line VL2 is positioned outside in the tube width direction ZD of the core plate 21.

Here, the first virtual line VL1 is a straight line extending along the flat surface of the inclined portion 215, and is a straight line indicated by an one-dot chain line in FIG. 7. In detail, the first virtual line VL1 is a straight line extending linearly along the inclined portion 215 from the receiving portion 212 toward the tube joint portion 211. As described above, the flat surface of the inclined portion 215 is substantially flat, and the flat surface may include minute steps, and irregularities, etc. formed in manufacturing.

The second virtual line VL2 is a straight line extending along a flat surface of the tube joint portion 211, and is a straight line indicated by a two-dot chain line in FIG. 7. Specifically, the second virtual line VL2 is a straight line extending linearly along the tube joint portion 211 in a direction of a long diameter in a cross section of the tube 11 (that is, a long diameter direction in the cross section). As described above, the flat surface of the inclined portion 215 is substantially flat, and the flat surface may include minute steps, and irregularities, etc. formed in manufacturing.

Returning to FIG. 2, the tank body portion 22 according to the present embodiment has a part, in which a length in the tube width direction ZD is shorter than a length in the tube width direction of the tube 11 in order to reduce a thinning in the tube width direction ZD of the radiator 1. A part facing the tube 11 in the tank body portion 22 is provided with a protruded portion 221 protruding away from the tube 11 in the tube width direction ZD. So, an inner side of the tank body portion 22 is configured to be in non-contact with the tube 11.

The tank body portion 22 in the present embodiment has a flange portion 222 having a thickness larger than that of the other part and is positioned at a tip part adjacent to the core plate 21. The flange portion 222 is disposed in the receiving portion 212 of the core plate 21 via the packing 23.

Next, an outline regarding a method for manufacturing the radiator 1 with the above configuration is explained. The manufacturing method for the radiator 1 in the present embodiment includes a preparation step, a temporary assembly step, and a brazing joining step. First, in the preparation step, each component constituting the radiator 1 is prepared. The preparation step includes a forming step for forming the core plate 21 having the tube joint portion 211, the receiving portion 212, the protruding parts 213, and the rib 214. In the present embodiment, the tube insertion hole 211 a is formed on the flat surface of the tube joint portion 211 by means of a process for punching plate-like metal material (for example, a punching process).

Subsequently, in the temporary assembly step, the tube 11, the fin 12, and the side plate 40 prepared in the preparation process are assembled in the tube stacking direction YD on the working table such that the core portion 10 etc. are temporarily assembled.

In the temporary assembly step, the core plate 21 on which the tube insertion hole 211 a is formed is assembled to the core portion 10 and then an assembled state is maintained by a jig such as a wire. Subsequently, in the brazing joining step, an assembled body in assembled state in which the core plate 21 is assembled to the core portion 10 is placed in a heated furnace such that the core plate 21 and each element of the core portion 10 are joined by brazing.

After a completion of the brazing joining step, the packing 23 is housed in the receiving portion 212 of the core plate 21. The flange portion 222 of the tank body portion 22 is housed in the receiving portion 212 in which the packing 23 is housed, and the tank body portion 22 is caulked and fixed to the core plate 21 by plastically deforming each of the protruding parts 213 by a press working or the like.

Subsequently, the manufacture of the radiator 1 is completed through an inspection process for performing a leakage inspection, a dimension inspection, and the like. The leakage inspection or the like confirms whether or not a poor brazing or the like has occurred at a joint portion of each of the components.

The radiator 1 in the present embodiment provided with the above-described configurations has the following advantages. In the radiator 1 of the present embodiment the tube joint portion 211 of the core plate 21 and the bottom wall portion 212 a of the receiving portion 212 are connected through the inclined portion 215. In this configuration of the radiator 1, even if a thickness in the tube width direction ZD of the core plate 21 is thinned, it can be prevented from being joined at unintended positions between the tube 11 and the core plate 21.

In particular, in the present embodiment, as shown in FIG. 7, the inclined portion 215 is formed in such a manner that the first virtual line VL1 extending along the inclined portion 215 and the second virtual line VL extending along the tube joint portion 211 intersect outside in the tube width direction ZD of the tube 11. In the tube width direction ZD, the inclined portion 215 is formed at a position away from the tube insertion hole 211 a. Therefore, it is possible to suppress an occurrence of a recess formed on the peripheral part of the tube insertion hole 211 a in the core plate 21 by the molding shrinkage when the tube insertion hole 211 a is manufactured.

Accordingly, in the radiator 1 of the present embodiment, even if the thickness in the tube width direction ZD of the core plate 21 is thinned, it is possible to suppress the occurrence of unintended recess on the core plate 21. As a result, since a wraparound of the brazing material is stabilized in a case that the tube 11 and the core plate 21 are brazed and joined, a joining state between the tube 11 and the core plate 21 can be stabilized.

Here, due to a temperature difference occurred between adjacent tubes 11, as shown in FIG. 8, the core plate 21 is deformed as a bow shape, because the tube 11 on the high temperature side extends in the tube longitudinal direction XD. In this case, the stress concentrates at the end part in the tube width direction ZD of the tube 11.

Thus, in the present embodiment, the recessed rib 214 is formed between adjacent ones of the tube insertion holes 211 a in the core plate 21 and formed to be positioned on an end part in the tube width direction ZD of each tube 11, and is formed so as to be away from the end part in the tube longitudinal direction XD of each tube 11.

According to the above configuration, when the temperature difference occurs between adjacent tubes 11, a deformation on the end part in the tube width direction ZD of the tube insertion hole 211 a, namely a thermal distortion, can be suppressed by the rib 214. So, the stress concentration at the end part in the tube width direction ZD of the tube 11 can be prevented.

The stress concentration generated at the end part in the tube width direction ZD of the tube 11 is also suppressed, because the inclined portion 215 which is located outside in the tube width direction ZD of the tube 11 is deformed around the intersection A. In other words, when the temperature difference occurs between adjacent tubes 11, the stress generated at the end of the tube 11 in the tube width direction ZD of the tube 11 is absorbed by the deformation of the inclined portion 215.

However, as shown in a comparative example of FIG. 9, since a part of the inclined portion 215 is overlapped with the tube insertion hole 211 a in the tube longitudinal direction XD, a volume of a part in the inclined portion 215 for absorbing the stress is reduced. As a result, the effect of reducing the stress generated at the end part in the tube width direction ZD of the tube 11 due to the deformation of the inclined portion 215 cannot be sufficiently obtained.

So, the present inventors studied an effective range which shows a reduction of the stress concentration acting on the end part of the tube 11 in the tube width direction ZD of the tube 11 in relation with a position of an intersection A between the first virtual line VL1 and the second virtual line VL2.

FIG. 10 is a diagram illustrating an examination result regarding the effective range which shows the reduction of the stress concentration acting on a tube root portion Tb with respect to a distance Lta between the tube root part Tb (an end part in the tube width direction ZD) of the tube 11 and the intersection A.

The horizontal axis in FIG. 10 designates a distance between the tube root portion Tb and the intersection A, that is, the tube-intersection distance Lta. On the other hand, the vertical axis in FIG. 10 designates a generated stress ratio in which the stress acting on the tube root portion Tb represents 100% when the tube-intersection distance Lta is set to 0 (zero).

In FIG. 10, the triangle plots show a relationship between the tube-intersection distance Lta and the generated stress ratio, when an inclination angle θ (theta) of the inclined portions 215 is set to 15 degrees. The square plots show a relationship between the tube-intersection distance Lta and the generated stress ratio, when the inclination angle θ (theta) of the inclined portions 215 is set to 20 degrees. Further, the diamond plots show a relationship between the tube-intersection distance Lta and the generated stress ratio, when the inclination angle θ (theta) of the inclined portions 215 is set to 40 degrees. The inclination angle θ (theta) is defined as an angle between the inclined portion 215 and the tube longitudinal direction XD, as shown in FIG. 7.

As shown in FIG. 10, when the tube-intersection distance Lta is between 0.0 and 2.4 mm (that is, 0.0≤Lta≤2.4), the stress acting on the tube root part Tb is reduced. It is also found that the same tendency is obtained, even if the inclination angle θ (theta) is changed.

Here, as shown in the comparative example of FIG. 9, the configuration in which the tube-intersection distance Lta is negative is characterized in that a part of the inclined portion 215 is overlapped with the tube insertion hole 211 a in the tube longitudinal direction XD. Therefore, the strength of the inclined portion 215 is increased, and it is considered that the effect of reducing the stress acting on the tube root part Tb cannot be sufficiently obtained.

In a configuration in which the tube-intersection distance Lta exceeds 2.4 mm, a thickness between the inclined portion 215 and the tube 11 in the tube width direction ZD is increased. Therefore, the strength of the inclined portion 215 is increased, and it is considered that the effect of reducing the stress acting on the tube root part Tb cannot be sufficiently obtained.

Thus, it is preferably that the inclined portion 215 is provided on the core plate 21 in such a manner that the distance from the intersection A between the first virtual line VL1 and the second virtual line VL2 to the tube root part Tb is set to be between 0.0 and 2.4 mm, when viewed from the tube stacking direction YD.

When the tube-intersection distance Lta is set to be between 0.0 to 2.4 mm, the deformation of the end part in the tube width direction ZD of the tube 11 can be effectively suppressed, even if the temperature difference between adjacent tubes 11 occurs.

Here, when the tube-intersection distance Lta is 0.0, the generated stress ratio is 100% or less, but close to 100%. Therefore, it is preferably that the inclined portion 215 is provided on the core plate 21 in such a manner that the tube-intersection distance Lta is larger than 0.0 mm and is 2.4 mm or less.

In addition, when the tube-intersection distance Lta is set to be between 0.4 and 1.9 mm, the generated stress ratio is 80% or less such that the deformation of the end part in the tube width direction ZD of the tube 11 can be reliably suppressed.

Furthermore, when the tube-intersection distance Lta is set to be between 0.6 and 1.3 mm, the generated stress ratio is 60% or less such that the deformation of the end part in the tube width direction ZD of the tube 11 can be more reliably suppressed.

Here, in the present embodiment, the flange portion 222 constituting a tip part of the tank body portion 22 is caulked and fixed by the protruding part 213 of the core plate 21. In this configuration, the stress may be concentrated at the end side in the tube width direction ZD of the tube insertion hole 211 a when being caulked and fixed.

In the configuration in which the flange portion 222 constituting a tip part of the tank body portion 22 is caulked and fixed by the protruding part 213 of the core plate 21, it is preferable to adopt the core plate 21 in the above mentioned present embodiment.

Second Embodiment

Next, a second embodiment will be explained with reference to FIG. 11. FIG. 11 is a cross-sectional view showing main part of the core plate 21.

As shown in FIG. 11, in the present embodiment, a recess portion 216 is intentionally formed in such a manner that a step is formed between the inclined portion 215 and the tube joint portion 211. The recess 216 is configured to form a brazing filler pool for storing the brazing filler material between the tube 11 and the inclined portion 215, when the tube 11 and the core plate 21 are brazed and joined.

Other configurations are the same as those of the first embodiment. According to the present embodiment, the following effects are achieved in addition to the effects described in the first embodiment. In the present embodiment, since the recess 216 is formed between the inclined portion 215 and the tube joint portion 211, a joining strength between the end part in the tube width direction ZD of the tube 11 and the core plate 21 can be increased. Accordingly, when a temperature difference occurs between adjacent tubes 11, the deformation of the end part in the tube width direction ZD of the tube 11 can be more reliably suppressed.

Another Embodiment

The embodiments of the present disclosure is described above, however, the present disclosure is not limited to the embodiments described above, and can be appropriately changed. For example, various modifications can be made as follows.

(1) According to each of the embodiments described above, it is preferable that the burring portion 211 b and the rib 214 are provided on the tube joint portion 211. The burring portion 211 b and the rib 214 may not be formed on the tube joint portion 211.

(2) In each of the above embodiments, the protruded portion 221 is provided on the portion facing the tube 11 in the tank body portion 22, however the protruded portion 221 may not be provided.

(3) In each of the above embodiments, the heat exchanger in the present disclosure is applied to the radiator 1, but the present disclosure is not limited to the radiator. For example, the heat exchanger of the present disclosure may be applied to a refrigerant evaporator and a refrigerant radiator in a vapor compression type refrigerating cycle, and an intercooler for cooling the intake air in the internal combustion engine.

(4) In the above embodiments, it goes without saying that the constituent elements of the embodiment are not necessarily indispensable except for the case where it is clearly indispensable and the case where it is considered to be obviously indispensable in principle.

(5) In the above embodiments, when value regarding number, numerical values, quantity, or range, etc. of the components in the embodiments is mentioned, it is not limited to the specific value, except for the case where it is clearly indispensable and the case where it is clearly limited to a specific number in principle.

(6) In the above embodiments, when a shape or a positional relationship of the components is mentioned, it is not limited to the specific shape or the specific positional relationship except for the case where it is clearly indispensable and the case where it is clearly limited to a specific shape or a specific positional relationship in principle. 

What is claimed is:
 1. A heat exchanger, comprising: a core portion having a plurality of tubes formed as a flat shape and stacked with each other; and header tanks provided on an end part of the tube in a longitudinal direction of the tube and communicating with the plural tubes, wherein the header tanks comprises: a core plate brazed and joined to the plural tubes in a state that the end parts of the tubes in the longitudinal direction of the tubes are inserted in a plurality of tube insertion holes, and a tank body portion fixed to the core plate and forming a space communicating with the plural tubes together with the core plate, wherein the core plate comprises: a tube joint portion in which the plural tube insertion holes are formed, a receiving portion surrounding the tube joint portion and housing a tip part which is close to the core plate in the tank body portion, and an inclined portion connected between the receiving portion and the tube joint portion, and inclined with respect to the longitudinal direction of the tube, wherein  a first virtual line is defined as extending linearly along the inclined portion from the receiving portion toward the tube joint portion,  a second virtual line is defined as extending linearly along the tube joint portion in a direction of a long diameter in a cross section of the tube, and  the inclined portion is provided on the core plate such that an intersection between the first virtual line and the second virtual line is positioned outside of the tube in the width direction of the tube.
 2. The heat exchanger according to claim 1, wherein in the tube joint portion, the plural tube insertion holes are formed so as to be arranged at a predetermined interval in a stacking direction of the tube, and a rib is formed between adjacent ones of the tube insertion holes and in a position corresponding to an end part of the tube in the width direction of the tube, the rib being recessed away from an end part of the tube in the longitudinal direction of the tube.
 3. The heat exchanger according to claim 1, wherein a tube-intersection distance is defined as a distance from an intersection between the first virtual line and the second virtual line to the end part of the tube in the width direction of the tube in a stacking direction of the tube, and the inclined portion is provided on the core plate such that the tube-intersection distance is set to be between 0.0 and 2.4 mm.
 4. The heat exchanger according to claim 1, wherein a tube-intersection distance is defined as a distance from an intersection between the first virtual line and the second virtual line to the end part of the tube in the width direction of the tube in a stacking direction of the tube, and the inclined portion is provided on the core plate such that the tube-intersection distance is set to be larger than 0.0 mm and to be 2.4 mm or less.
 5. The heat exchanger according to claim 1, wherein the tip part in the tank body portion is caulked and fixed to the core plate in a state that the tip part is housed in the receiving portion.
 6. The heat exchanger according to claim 1, wherein the plural tube insertion holes are formed to be arranged at a predetermined interval in a stacking direction of the tube in the tube joint portion, and the inclined portion is provided to overlap respectively the plural tube insertion holes in the direction of the long diameter in the cross section of the tube.
 7. The heat exchanger according to claim 1, wherein a tube-intersection distance is defined as a distance from an intersection between the first virtual line and the second virtual line to the end part of the tube in the width direction of the tube in a stacking direction of the tube, and the inclined portion is provided on the core plate such that the tube-intersection distance is set to be between 0.4 and 1.9 mm. 